Apparently balanced de novo translocations in patients with abnormal phenotypes: report of 6 cases.

Six patients have been ascertained because of abnormal phenotypes but with apparently balanced de novo translocations. Five of them were mentally retarded with multiple congenital anomalies. The sixth patient had normal mental development but revealed ambiguous genitalia and multiple congenital anomalies. No syndromal diagnosis was possible in any of the six cases. The appearance of apparently balanced reciprocal translocations in association with abnormal phenotype may be coincidental, or the two may be causally related. If the latter is true, the causal relationship may be based upon: 1) a submicroscopic chromosomal loss, 2) position effect, or 3) a mutation at the site of the break in one or both translocated chromosomes.